Abstract
Three-dimensional Bi-chalcogenide topological insulators exhibit surface states populated by massless Dirac fermions that are topologically protected from disorder scattering1. Here, we demonstrate that these states can be enhanced or destroyed by strain in the vicinity of grain boundaries on the surface of epitaxial Bi2Se3(0001) thin films. Using scanning tunnelling and transmission electron microscopy, we show that the low-angle tilt grain boundaries in Bi2Se3(0001) films consist of arrays of alternating edge dislocation pairs. Along the boundary, these dislocations introduce periodic in-plane compressive and tensile strains. From tunnelling spectroscopy experiments and first-principles calculations, we find that whereas the energy of the Dirac state shifts in regions under tensile strain, a gap opens in regions under compressive strain, indicative of the destruction of the Dirac states at the surface. These results demonstrate that Dirac states can be tuned by strain at the atomic scale.
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Acknowledgements
Funding for this work is provided by NSF (DMR-1105839).
V.K.L. and P.L.G. thank the Royal Society International Exchanges Scheme for travel support and K. McKenna of the University of York for fruitful discussions.
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Y.L., Y.Y.L., S.R. and L.Li carried out the MBE growth and STM experiments. D.G., L.Lari., V.K.L. performed the TEM experiment. P.L.G. performed the strain analysis, M.W. performed the DFT calculations. All authors contributed to the analysis and interpretation of the data. L.Li, M.W., and V.K.L. wrote the paper.
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Liu, Y., Li, Y., Rajput, S. et al. Tuning Dirac states by strain in the topological insulator Bi2Se3. Nature Phys 10, 294–299 (2014). https://doi.org/10.1038/nphys2898
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DOI: https://doi.org/10.1038/nphys2898
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